Royal canin 33 is perfect till your baby hits 10 months, then the yorkie formula of Canin. MY ava was on purina 1 when i got her at 8 weeks, i put 1/2 Royal canin & 1/2 prina. guess what? she only ate the royal canin so not gradual for her but usuallt it is gradual. must be the peke in her lol, Sorry if my writing is off today, my 31/2 yr old grandson and ava r both at my feet!